There is an increasing interest in printing machine-readable variable data, including time-dependent data (e.g., a freshness date) and serialized data (e.g., a lot number) on retail items. One way of printing time-dependent data at production line speeds is ink jet or laser printing (e.g., printing lot number and date on cans and bottles). However, the dimensional imprecision of the resulting labels inhibits robust automatic data capture.
Several “dot codes” are known in the art which define symbols composed by multiple dots. However, the symbols defined by the known “dot codes” are generally of a square form, with heights exceeding the limits supported by high speed ink jet printers. Although not technically a dot code, but sometimes printed as one, Data Matrix ECC 200 bar code includes several versions with the symbol height being 8 and 16 dots, but the symbols have fixed limited length and hence limited data capacity, and also are not fundamentally tolerant to printing irregularity.
Hence, a need exists to provide a machine-readable two-dimensional symbology with a limited symbol height. There is a further need to provide a machine-readable two dimensional symbology the design features of which assure that the symbol orientation can be unambiguously determined. There is a further need to provide a machine-readable two dimensional symbology which is robust and secure when printed by high-speed inkjet or laser dot printers.